Portable handheld RF communication devices such as cellular telephones, portable radios, data communication devices, and the like employ a radiator or antenna to radiate and receive RF signals. Monopole antennas are widely used as RF radiators in such devices. As such communication devices become more complex, e.g. by the incorporation of additional functional components such as cameras, advanced loudspeakers, and the like, extra functional requirements are imposed on the radiator system. There is also an ongoing search for ways to reduce the overall size and weight of such devices, including the radiator system.
Thus, it is expected in the future that the space available in a portable communication device for the radiator will decrease, since the overall size of the device will continue to decrease and/or the device will have to accommodate other functional components at the expense of the radiator. However, reducing the radiator size may negatively impact radiator gain and bandwidth. This follows from the fact that a radiator is used to transform a bounded wave into a radiating wave. However, when the dimensions of the radiator are much smaller than the wavelength of the RF radiation to be transmitted, the radiator performs this transformation with only a poor efficiency. The loss in radiator gain can to some extent be compensated for by amplification. However, this causes a greater energy consumption, e.g. from a battery of the device.
Another challenging task is that the distance available between the radiator and other components of the communication device, such as a camera unit or an advanced loudspeaker, is likely to be reduced as well. This requires careful selection of where components are placed in the communication device to give suitable operation of the radiator.
Thus there is a need for a new radiator (antenna) which addresses the above problems.